Electrical power is one of the fundamental requirements of modem society. Whilst electricity can be generated in many ways including photovoltaic cells, wind turbines or hydropower, most of the generation is accomplished using steam turbines to ensure that there is a steady continuous production of power. To generate steam large boilers are used to boil water with the heat produced by burning fossil fuels or nuclear fission.
Existing steam turbines are typically large, generating IOOkW+ to overcome losses and be financially viable. Expansion of steam requires increase in flow area in multiple stage axial and radial designs, while high pressure, temperatures and rotational velocity limit materials selection. Large size and generally horizontal configuration requires that the shaft be supported along the axial direction. Rotating blade rows (rotors) must be separated by stationary nozzle rows (stators), increasing complexity of assembly.
The development of power generation devices over the years which use steam as a motive fluid has primarily been focused on reducing the monetary cost per MW-hour of electricity generated. To that end, improvements in steam turbine technology have been focused on increasing the output, steam/boiler temperature, unit reliability/availability, or a combination of these. These improvements generally add to the unit cost, necessitating an increase in power output to remain fiscally viable.
Solar heated water has been known to be used to create steam and be used as an auxiliary energy input to drive an axial turbine that is comprised of a stationary row of airfoils (typically referred to as “nozzles”, “stators” or “vanes”) that accelerate and direct the fluid flow to impinge against a rotating row of airfoil shapes (typically referred to as “buckets”, “rotors” or “blades”) which are connected to a shaft for delivering power output to a connected device.
When the fluid density is very high at turbine inlet then it is common practice to design the first stage (and possibly the first few stages) of a multi-stage turbine, with “partial admission”. Partial admission refers to a stage design where nozzle passages are only provided for a portion (i.e., segment) of the 360 degree circumference. The main advantage of partial admission as used in conventional designs is that it enables the use of larger nozzle and blade passage heights (i.e., radial lengths) resulting in better efficiency due to reduced losses. This is especially important for high density flows where in a partial admission turbine the blade heights can be quite small.
In conventional turbines, particularly steam turbines, partial admission is only applied to the first stage (or first few stages) that operate with high density fluid. Subsequent stages cannot utilize partial admission because their operating pressure and density has been significantly reduced. As a result, a larger increase in nozzle and blade passage areas is required to compensate for the higher volume flow rate that occurs as the steam expands from inlet to exhaust. For these higher volume flow stages, full admission (360 degree) is typically required in order to achieve larger passage areas while maintaining blade heights within reasonable mechanical stress limits.
When the steam has passed through all of the stages any remaining steam needs to be condensed so it can be removed as water from the bottom of the turbine. Typically the condensed water may be reused in the steam generator.
It is an object of the present invention to provide a system for generating electrical power from low temperature steam for use with a partial admission steam turbine. For details of the separate components the reader is referred to co-pending applications titled:                (a) A method and apparatus for generating low temperature steam from hot water for use with a multi-stage axial flow turbine adapted to operate at low steam temperatures.        (b) A multi-stage axial flow turbine adapted to operate at low steam temperatures.        (c) A shaft for use with a multi-stage axial flow turbine adapted to operate at low steam temperatures.        (d) A condenser system for use with a multi-stage axial flow turbine adapted to operate at low steam temperatures        